An oscillator is a circuit which originally used electron tubes but now normally uses individual transistors or gates to generate an AC output signal. The frequency of the signal generated may be quite low for audio oscillators or quite high for rf, microwave oscillators and the like. There are many applications for oscillators such as signal generators, frequency standards, transmitters, receivers and the like.
Although oscillators perform definite functions in various circuits, in all instances they are considered to be devices which are used for the purpose of generating signals having specific frequencies.
Currently there are numerous designs for oscillator circuits which use semiconductor devices, one of which is the Pierce oscillator. The pierce oscillator can be built using CMOS, TTL or ECL gates both as an amplifier and to provide the appropriate output signal. CMOS is normally used for low frequencies, TTL is normally used for medium frequencies, and ECL in used for both medium and high frequencies. Frequently, to obtain relatively high frequency signals, a Pierce oscillator will be operated as a harmonic oscillator.
The Pierce oscillator circuit provides outstanding operating characteristics. For example, the waveform and stability are good, variations of power supply or temperature have little effect on the frequency of the signal obtained, and it provides a relatively high output potential. A manor disadvantage of the Pierce circuit is that it requires a relatively large number of components.
A new improved oscillator is required which satisfies the constraints of integrated circuits size and parts count limitations required to satisfy not only the space and cost limitations of todays integrated circuit manufacturing technologies, but also has the outstanding performance characteristics of a Pierce type of oscillator.